Due to the fact that carbonated spring has good thermal insulation effect, it has been utilized in thermal spring baths and so on. It is substantially considered that the thermal insulation effect of carbonated spring is resulted from the dilatation effect of distal blood vessels containing carbonic acid gas, which improves the body environment.
In addition, as carbonic acid gas enters into the body percutaneously, the capillary bed increases and dilates, and thereby the skin blood circulation improves. Therefore, it has good therapeutic effects on degenerative pathological changes of organs and peripheral circulation blockage.
Carbonated spring has been reported in various articles (e.g., see non-patent document 1 and non-patent document 2).
As indicated in non-patent document 1, through repetitive observations by thermal spring doctors in early stage for major direct effects of carbonated spring, Bode of Bad Nauheim observed hyperemic, velutinous, and rubescent skin (1845); Piderit (1836) and Beneke (1859) stated mitigative sense in carbon dioxide bath and rubescent skin on the bathed part; and Goldschieider discussed in 1911 that the rubescent skin stimulated by carbonic acid was possibly caused by movement of blood vessels.
In addition, as indicated in above articles, two impressive direct effects of carbonic acid bath were observed. One effect is that there are numerous water bubbles on the skin; and the other effect is ruddy skin (according to Usui's Ischemic Demarcation theory, the immersed part can be distinguished apparently from the non-immersed part). The water bubbles are numerous carbonic water bubbles, which contact closely with the skin and have effect of “gas brush”.
Furthermore, as indicated in non-patent document 2, the minimum concentration of carbonic acid gas required for therapy is 400 mg; however, as indicated in non-patent document 1, ruddy skin occurs when the concentration of carbonic acid gas reaches to 400 mg.
Since carbonated spring has such good effects, people have been developing the producing method of carbonated spring. Wherein, a method was mentioned in patent document 1.
The producing method of carbonated spring mentioned in patent document 1 was: feeding warm water into a carbonic acid gas dissolver with gas dissipation apparatus, releasing carbonic acid gas as bubbles and dissolve the bubbles in the warm water by using the gas dissipation apparatus immersed in the warm water, so as to produce carbonated spring. After the carbonic acid gas is dissolved in the warm water in said carbonic acid gas dissolver under pressure, the obtained carbonated spring is sent to a gas separator to reduce the pressure to normal pressure, the carbonic acid gas volatilizing from the carbonated spring is guided to a compressor for recovery by the gas separator, and the recovered carbonic acid gas is guided to above carbonic acid gas dissolver and dissolved in the warm water.
However, in the producing method of carbonated spring mentioned in patent document 1, a gas dissipation apparatus is required. Above gas dissipation apparatus has a porous part, by which the carbonic acid gas is formed into a large amount of bubbles and is dissolved in the warm water.
In addition, other known gas dissipation apparatuses include: an apparatus with a hollow linear membrane assembly designed to enclose a perforated tube with front part blocked; wherein, the warm water flowing into the perforated tube flows out from the holes on the perforated tube and contacts with the hollow linear membrane, so that the carbonic acid gas injected from the guide port through the hollow part of the hollow linear membrane is dissolved in the warm water.
Accordingly, fine particles (e.g., impurities) in the warm water may block the porous part or the hollow linear membrane of the gas dissipation apparatus; as a result, the gas dissipation apparatus has to be cleaned or replaced frequently, which is very time-consuming.
Furthermore, since carbonic acid gas bomb, gas separator, and compressor, etc. are required, the apparatus is large in size and high in cost.
In addition, since the producing method of carbonated spring of the prior art utilizes a carbonic acid gas bomb to dissolve the pressurized carbonic acid gas in water, the carbonic acid gas not dissolved in water is directly released to the atmosphere uselessly, which deviates from the carbonic acid gas reduction tenet in recent years, and causes adverse effect to the global environment.
A known method of producing carbonic acid gas in aqueous solution without the use of a carbonic acid gas bomb is to utilize a bath agent mixed with a carbonic acid gas generator consisting of carbonate and acid (e.g., see patent document 2).    Patent document 1: Japanese Unexamined Patent Application Publication No. Hei 11-192421    Patent document 2: Japanese Unexamined Patent Application Publication No. 2005-97238    Non-patent document 1: K. L. Schmid., Carbonated Bath (Carbonated Spring), Magazine of Artificial Carbonated Spring Research Association, 1998, 1(1): 005˜009.    Non-patent document 2: B. Hartman, M. Pittler, B. Drews, Carbon Dioxide Thermal Spring Recuperation for Arteriolar Blockage Patients: Physiology and Clinic, Magazine of Artificial Carbonated Spring Research Association, 1998, 1(1): 010˜016.